Art of treating ores.



. UNITE ta-res ATENT, truce.

ROBERT MoKNIGl-IT, OF PHILADELPHIA, PENNSYLVANIA.

ART OF TREATING ORES.

SPECIFICATION forming part of Letters Patent No. 696,469, dated April 1, 1902.

Application filed August 10,1901. Serial No. 71,607. (No specimens.)

To all whom it may concern:

Be it known that 1, ROBERT MOKNIGHT, a citizen of the United States, and a resident of the city and county of Philadelphia and State of Pennsylvania, have invented a new and useful Improvement in the Art of Treating Ores, of which the following is a full, clear, and suiiicient specification, reference being had to the drawings annexed.-

My invention has reference to the art of treating ores of the precious metals when a portion of the metal is in a finely-divided state called fiour gold or silver and where other parts of the metal are in the form of nuggets-that is, in particles having an appreciable though not necessarily large size. The object of my invention is to convert the Hour metal into a haloid or oxyhaloid salt of the precious metal and to remove from the surface of the nuggets the coating that is found thereon and which would prevent them from being amalgamated when passed over the amalgamation-plates or through other amalgamating apparatus, in which passage hitherto much of the precious metal has been lost. The precise treatment varies some what with the different ores and with the coating upon the particles or nuggets that are subsequently to be amalgamated, and is ap plicable as well to free-milling as to refractory ores, the latter, however, containing the material that has to be supplied to the freemilling ores. The element sulfur is the one generally of the so-called refractory elements that is present, though arsenic, tellurium, or selenium may be present or introduced into the ore for the purpose of carrying out my process. These materials will react with a haloid salt of an alkaline or alkaline-earth metal to produce the reaction desired. This haloid salt of the alkaline or alkaline-earth metal is mixed with ore. The coatings on the particles that are to be treated by amalgamation also vary apparently. They are considered by many to be organic matter-that is, compounds containing oxygen, hydrogen, and carbon-by others carbonates, but of what metal there has been no sufficient determination to speak positively. Others consider them to be sulfids or silicates. If either of the first two suppositions or the last are correct, there would be one more reaction than there would be with the next to last supposition; but in both cases the method of treatment can be substantially the same. In the first two cases the carbonicacid radical is displaced by the sulfur or its analogue, and the sulfur then combines with the oxygen and the alkaline or alkaline-earth metal to form a stable oxysalt of the same, leaving the halogen free in a nascent state to combine with the precious metal in a flour state. If the first supposition is not correct and the next to last supposition is true, the first-mentioned reaction does not take place. The reaction by which the sulfur unites with oxygen and the alkaline or alkaline-earth metal cleans the particles or nuggets.

Describing now in detail the best method of which I am at present aware of carrying out my invented art, I mix with the ore which has been pulverized, or mix with the ore and pulverize the same, a haloidsalt of an alkaline oralkaline-earth metal and, if the ores are not refractory, a sufficient quantity of sulfur or an analogue thereof, either native or in a suitable combination, such as iron or copper pyrites. In practice the ore if freemilling will be mixed with another ore containing iron pyrites. In a refractory ore of course the pyrites are not required to be mixed with the ore. The quantity of each material will vary with the kind oflore treated and will be calculable when the approximate amount of the various materials in the ore are known. The following rules canbe laid down from which a practical mining man can readily determine the requisite amounts of each material required.

In case carbonates are contained in the ore there must be enough sulfur or its. analogue to displace the carbonic-acid radical, there must be enough of the halogen to convert the precious-metal values that exist in the form of flour metal into haloid or oxyhaloid salts, and there must be enough of the alkaline or alkaline-earth metals to cause the substantially entire amount of the refractory metalloids to combine with them and with oxygen to form the stable oxysalts of the alkaline metals and the refractory metalloids above mentioned. I/Vhere the quantity of refractory metalloids in the ore is so small that the formation of the oxysalts above mentioned. will not set free sufficient quantity of the halogen to form the flour metal into haloids and to cleanse the larger particles, an additional supply can be furnished to the ore by adding a suitable material, such as pyrites. To produce these reactions, the ore is heated in practice, unless materials such as Chili saltpeter or other suitable nitrate are introduced to lessen the required heat, to about 900 centigrade, preferably in a receptacle admitting a free access of air, but closed against the products of combustion, and with an outlet and conductor for leading the volatilized products of the reaction from the furnace to a condenser. This prevents the volatilized products of the reaction from becoming mixed with the fumes of the combustion and also from reacting in any way with them. In the open furnace the products of the reaction are separated from the products of the combustion by blankets, collections from the chimney, or from water-baths, into which the entire body of the fumes are passed. An open furnace can, however, sometimes be used to advantage when gas or oil is used as the fuel, as it is comparatively easy to remove the fumes from the products of combustion of these fuels.

The reactions that take place arecertainly the following: The sulfur or its analogue unites with the oxygen and the alkaline or alkaline-earth metal to form a stable oxysalt, and the liberated halogen (in practice chlorid) in a nascent state unites with the flour metal and forms a haloid or an oxyhaloid salt of the same. This is volatilized and passes ofi. The halogen thus liberated also acts upon the coating on the surface of particles in the ore of larger size, provided the same has not been previously completely removed by the previous action of removing the sulfid therefrom.

The following is an illustration of the reactions that can be considered as taking place in this ore treatment. First phase:

2CaCO +2FeS +2O =2OaSO +2CO +Fe O and two reactions taking place simultaneously to form the second phase: 3O+3OaCO +6NaCl+Au 3Na SO +2AuCl +3CaQ 'If the particles of the precious metal are coated with a carbonate, the sulfur or other refractory metalloid unites with it and the carbonic-acid radical is eliminated and the coating becomes a sulfid, which in turn is acted upon in the reaction in which the haloid salt of the alkaline or alkaline-earth metal is disassociated and the sulfur forms with oxygen and this said alkali or alkali-earth metal an oxysalt, as above described, any oxid that takes the place of the sulfid on the surface of particles or nuggets being friable and readily removes by attrition. During all these processes the ore is rabbled or otherwise agitated, if practicable.

The volatilized haloids of the precious metals are collected and the metal values recovered, While the ore containing the nuggets is carried over the amalgamating-pans, and the larger particles are collected. As the particles of the precious metals are now perfectly clean, all the metal Values are collected practically without loss.

Having now described my invention, what I claim, and desire to secure by Letters Patent, is

1. The art of treating ores containing precious metal in a flour state and also in larger particles, which consists in heating with free access of air and agitation, a mixture of the ore, containing a refractory metalloid and a haloid salt of an alkaline or alkaline-earth metal, until a haloid salt of the precious metal is produced and volatilized and the coarser particles of the preciousmetal have their surface coatings removed, and the alkaline or alkaline-earth metal unites with the oxygen of the air and with the refractory metalloid, to form a stable oxysalt, collecting the volatilized haloid or oxyhaloid of the precious metals, and treating the cleaned particles by amalgamation, substantially as described.

2. The art of treating ores which contain precious metals in a flour state and also in larger particles, coated with carbonates which consists in heating a mixture of the ore a refractory metalloid, and a haloid salt of an alkaline or alkaline-earth metal, with free access of air and agitation, until the carbonicacid radical of the carbonate upon the surface of the larger particles is driven off, and the material formerly in combination therewith is changed into a sulfidor sulfate and continuing the heating until these sulfids are changed into oxids, and the haloid salt of the alkaline or alkaline-earth metal is decomposed, and the nascent halogen combined with the finer particles of the precious metals, and the alkaline or alkaline -earth metals combined with oxygen and the refractory metalloid to form a stable oxysalt of the re- IIO fractory metalloid, and the alkaline or alka- 

